Globally, many people clean fabrics by hand washing or machine-assisted hand washing with compositions containing soap and/or detergent. Machine-assisted hand washing of fabrics involves the use of a manual or semi-automatic wash machine with completion of the wash process and later, rinse the fabrics by bucket or in machine spinner.
In the normal washing process, water is taken in a bucket or in fabric's soaking container or washing tub of semi automatic machine. Thereafter, desired quantity of detergent is added to generate lather by hand shaking or run for a while the washing tub in semi-automatic machines. This is followed by immersion of the dirt fabrics for soaking for 10 to 30 min. After soaking period, the fabric is rubbed by hand to remove dirt or the washing cycle is run for 10 to 20 min in case of semi-automatic machines.
For rinsing, the dirt water is drained out and by squeezing the dirt water is removed from fabrics. Thus each such rinsing cycle consists of squeezing the fabrics and washing the fabrics with fresh water. Such rinsing cycle is repeated for four to five times for hand wash or in case of semi automatic machine, four to five times rinse cycle is followed to remove all foams before final spinning.
Effective hand wash detergent compositions comprise anionic surfactants, particularly alkylbenzene sulfonate and alkyl sulfate surfactants. It has also been found beneficial for the appearance and cleaning of fabrics for hand wash laundry detergents to contain an amount of a cellulase enzyme sufficient to improve the appearance and cleaning of such fabrics, particularly after multiple cleaning cycles. But this anionic surfactant is important for cleaning and cheap source of generating substantial foam in the washing even at small amount.
Globally, water pollution and water conservation are serious concerned specially in the developed and underdeveloped countries. In Asia, countries like India, China, Indonesia, Thailand, Vietnam more than 80% people wash their cloths by hand. In Latin America, countries like Brazil, Colombia, Venezuela and Argentina more than 70% people follow hand washing to clean their cloths. Hand washing of cleaning the cloths is also predominating in Eastern Europe and Africans countries. During cleaning of fabrics by hand washing or by semiautomatic machine, huge amount of clean water is used during the rinsing where rinsed water contains ppm level of detergent. The ppm level of residual detergent doesn't make any discomfort during the use of washed garments/cloths in real life but it is a human way of mind to believe that generation of foam during rinsing means dirt detergent is still entrapped in the clothes and more washing is necessary. So, user continues rinsing till rinsing liquor free from foam by following a standard rinsing sequence by hand washing in an order of rinsing the fabrics first, followed by squeezing the fabrics and draining out the rinsed water and again following the same cycle. At the end of washing, it is estimated that an excess of 50% or more water is drained out as a waste water which not only generates huge amount of waste water but also is unnecessarily use up fresh water for such rinsing only due to foam generation. On the other hand, it is clear that we are not only draining out the water but also draining out a huge amount of money for waste water treatment and also spending money to generate fresh water. Moreover, un-necessary use of valuable water for such hand washing/purposes is social evil in the country or region where scarcity of fresh water is massive.
On the other hand, detergent used in hand washing/semiautomatic machine wash, must have preferred foaming in nature during the soaking and washing process. It is important due to the fact of traditional concept of no foam means not a good detergent. So, all detergent manufacturers have a common requirement of foaming during washing and no foaming during rinsing that claims of saving cost and water of such kind of detergent.
In general, for foaming and de-foaming, two types of chemicals are available. Chemicals having defoaming activity has a mechanism to reduce foam or no foam when use in a liquid or solid and other types of chemicals having foaming tendency generate huge foam during the use in its application.
Attempts have been made in the past to resolve this problem by secondary method, called single rinse concept where during rinsing cycle, use a defoamer containing fabric conditioner where fabric conditioner conditioned the fabric at rinsing cycle and in addition kills the all residual foam. This concept was not very much successful in case of hand washing process, since use of fabric conditioner in this class is considered to be a luxury and people of hand-washing segment uses hand washing due to money constraint for fabric cleaning.
Considering the wastage of water and cost of normal detergent used in hand wash or semi-automatic machine, there has been the need for detergent formulations which when used for washing fabrics and the like would generate preferred amount of foaming during washing cycle without affecting the cleaning nature of the detergent but also have defoaming activity in rinsing cycle so that one or two rinse is enough to clean the fabric. It is however extremely difficult to provide for such characteristics in detergent formulations and the like which would favour both the washing and rinsing cycles and make washing of clothes/fabrics more convenient and user friendly apart from taking care of avoiding unnecessary wastage of valuable water and saving the environment from unnecessarily wastage of water in hand wash and/or semi automatic machine washing and the like. It is also important that such advancement directed to washing formulations adapted for effective washing avoiding wastage of water is attended at cost-effective rates since the market is very much price sensitive and the success of new detergent heavily depend on cost as well.
U.S. Pat. No. 4,637,890 disclosed a detergent composition that acts as defoamer in rinsing cycles. Detergent composition revealed a composition for suds/foams controlling prills comprising fatty acid soap, quaternary ammonium salt and silicone fluid for suds suppresser. It is indicated in the patent that the prills dissolve in the relatively high pH (from 9 to 10.5 pH) in washing cycles and prills are not active at high pH. Prills become active to suppress suds at low pH with a concept of lower pH at rinsing cycles where detergent contained less in rinsed water. However, the examples didn't direct to any actual applications and additionally it was not clear whether the detergent was effective in hand washing or machine-assisted hand washing. It is understood from the disclosure that effectiveness of suppressing foam by silicone defoamer was highly dependent on prills formation with the help of fatty acid soap and quaternary ammonium compound. According to the disclosure a normal silicone fluid (alkylated polysiloxane) used as defoamer where normal silicones defoaming activity was controlled in washing cycle by way of insolubility of prills at alkaline pH.
U.S. Pat. No. 4,894,117 disclosed a composition of agglomerated granules for the delay release of antifoaming agent in laundry system. It relates to a laundry detergent composition comprising silicone antifoam adsorbed on a powdered water soluble carrier selected from modified cellulose carriers which is subsequently agglomerated into granular form by mixing in presence of a solvent for the carrier. This prior art disclosed a series of granulated laundry additives wherein standard silicone antifoam were encapsulated. These different granulated laundry additives have different silicone antifoam release time depending on type of cellulose used and size of the granules. It is clearly apparent that such type encapsulated laundry additive is only suitable for machine wash but totally not suited in case of hand washing or machine-assisted hand washing since time of washing would vary from one user to another, one region to another region and one country to another country. Thus while a detergent composition having laundry additive granules with encapsulated silicone antifoam may be acceptable to one user but not suited to the requirement of another user due to different washing time where user can see no foam in washing cycles due to longer washing time or more water used in rinsing cycle due to shorter washing time since particular granules used in the detergent for washing would have a fixed time for releasing encapsulated silicones. According to the disclosure conventional silica filled polydimethyl siloxane used as defoamer to make encapsulated defoamer granules.
EP 254 499 B1 disclosed a method for the preparation of a silicone defoamer composition, said method comprising heating a mixture comprising    a blend of organopolysiloxanes (1) and (2)    (3) silanes or their partial hydrolysis condensates or siloxane resins,    (4) finely divided filler, preferably silica,    (5) reaction catalyst, preferably KOH,    (6) compounds like alkylene glycols, polyhydric alcohols, carboxylic acids and their esters, nonionic surfactants, polyoxyethylene anionic surfactants, polyether-modified silicones, nonionic fluorinated surfactants and OH-containing polymeric compounds like hydroxyethylcellulose.
A silicone defoamer composition is obtained by reacting a blend of trimethylsilyl-terminated polydimethylsiloxane and silanol-terminated polydimethylsiloxane with polyoxyethylene-polyoxypropylene copolymers and with silica.
The defoaming activity of the composition is disclosed but neither the use in a detergent composition is described nor can it be used as a delay defoamer by permitting foaming during the washing stage but inhibiting foaming during rinsing operations.
It is clear from the above state of the art that all such related arts depend on encapsulation of silicone or silicone defoamer where both the type of chemicals have strong antifoaming action.
The activity of delay defoamer or suppression of suds in rinsing cycles is dependent on many other parameters as discussed above. Therefore, application of such type of available defoamers is only possible in systematic washing system like machine wash but impossible to work in hand washing or machine-assisted hand washing because of wide variation of washing habit from one user to another user. On the other hand, any product that works in hand washing or machine-assisted hand washing, obviously performs better in all automated machine wash.
It is thus the basic object of the invention to develop modified organopolysiloxane based delay defoamer compounds/formulations that would easily mix with hand wash or semi automatic detergent and on one hand have no effect on detergency and preferred foaming nature of the detergent during washing cycle while on the other hand would provide excellent defoaming activity in the rinsing cycle.
Another object of the present invention is directed to provide a modified organopolysiloxane based delay defoamer compounds/formulations which will favour saving huge amount of fresh water and reduce the wastage of valuable water required in hand wash detergent or semiautomatic machine detergent applications for cloth/fabric washing.
Another objective of the present invention is directed to selective provision of modified organopolysiloxane based delay defoamer compounds/formulations for use in detergent formulation which would favour obtaining the much desired detergent formulation with advancement directed to washing formulations adapted for effective washing avoiding wastage of water at cost-effective rates.
Another objective of the present invention is directed to synthesize modified organopolysiloxane based delay defoamer compounds/formulations in simple way to optimise the cost of the organopolysiloxane compound that would have minimum impact in the formulation cost of final detergent.
Yet another object of the present invention is directed to a detergent composition/agent with excellent anti-foaming effect during rinsing while generate preferred foaming in washing cycle.